Filtration system with modularized energy recovery subsystem

ABSTRACT

A filtration system has a plurality of filtration modules disposed within an outer casing, which produce both a low pressure filtrate and a high pressure waste fluid from a pressurized feed fluid. The subsystem used to pressurize the feed fluid is mechanically coupled to the subsystem used to recover energy from the waste fluid such that energy in the high pressure waste fluid is used to pressurize the feed fluid. The pressurization and energy recovery subsystems are preferably coupled using a common drive shaft and at least one of the pressurization and energy recovery subsystems may advantageously contain a turbine.

This application claims the benefit of provisional No. 60/087,615 filedJun. 2, 1998.

FIELD OF THE INVENTION

The field of the invention is filtration systems.

BACKGROUND OF THE INVENTION

Filtration systems often require substantial pressure to drive a fluidthrough a membrane or other filter. In the case of reverse osmosissystems, this pressure requirement can translate into a substantialenergy cost or “penalty.”

It is known to mitigate the energy cost of filtration pumping byemploying a work exchange pump such as that described in U.S. Pat. No.3,489,159 to Cheng et al. (January 1970) which is incorporated herein byreference. In such systems, pressure in the “waste” fluid that flowspast the filter elements is used to pressurize the feed fluid.Unfortunately, known work exchange pumps employ relatively complicatedpiping, and in any event are discontinuous in their operation. Thesefactors add greatly to the overall cost of installation and operation.

It is also known to mitigate the energy cost of filtration pumping on acontinuous basis by employing one or more turbines to recover energycontained in the “waste” fluid. A typical example is included as FIG. 3in PCT/ES96/00078 to Vanquez-Figueroa (publ. October 1996), which isalso incorporated herein by reference. In that example, a feed fluid ispumped up a mountainside, allowed to flow into a filtration unit partwaydown the mountain, and the waste fluid is run through a turbine torecover some of the pumping energy.

A more generalized schematic of a prior art filtration system employingan energy recovery turbine is shown in FIG. 1. There a filtration system10 generally comprises a pump 20, a plurality of parallel permeators 30,an energy recovery turbine 40, and a permeate or filtered fluid holdingtank 50. The fluid feed lines are straightforward, with an intake line(not shown) carrying a feed fluid from a pretreatment subsystem (notshown) to the pump 20; a feed fluid line 22 conveying pressurized feedfluid from the pump 20 to the permeators 30; a permeate collection line32 conveying depressurized permeate from the permeators 30 to theholding tank 50; a waste fluid collection line 34 conveying pressurizedwaste fluid from the permeators 30 to the energy recovery turbine 40;and a waste fluid discharge line 42 conveying depressurized waste fluidfrom the energy recovery turbine 40 away from the system 10.

A system according to FIG. 1 may be relatively energy efficient, but isstill somewhat complicated from a piping standpoint. Among other things,each permeator 30 has at least three high pressure fluid connections—onefor the feed fluid, one for the waste fluid, and one for the permeate.In a large system such fluid connections may be expensive to maintain,especially where filtration elements in the permeators need to bereplaced every few years.

Thus, there is a continuing need for a simplified approach to recoveringenergy costs employed in pressurizing a filtration system.

SUMMARY OF THE INVENTION

The present invention is directed to filtration systems in which aplurality of filtration modules disposed within an outer casing produceboth a low pressure filtrate and a high pressure waste fluid from a feedfluid, and energy in the high pressure waste fluid is used to pressurizethe feed fluid.

In preferred embodiments the feed fluid is pressurized using apressurization subsystem, the energy in the waste fluid is recoveredusing an energy recovery subsystem, and the pressurization and energyrecover subsystems are mechanically coupled such that energy derivedfrom the energy recovery subsystem is used to drive the pressurizationsubsystem. In more preferred embodiments at least one of thepressurization and energy recovery subsystems utilize a turbine. Instill more preferred embodiments the pressurization and energy recoverysubsystems are coupled using a common drive shaft.

Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a prior art filtration system employing anenergy recovery turbine.

FIG. 2 is a schematic of a filtration system according to the presentinvention employing an energy recovery subsystem.

FIG. 3 is a schematic of a field of filtration systems according to thepresent invention.

DETAILED DESCRIPTION

In FIG. 2 a preferred filtration system 10 generally comprises apressurizing subsystem 120, a plurality of reverse osmosis or otherfilter modules 130, an energy recovery subsystem 140, and a permeate orfiltered fluid holding tank 150. Analogously to FIG. 1, a feed fluidfrom line 112 enters a pretreatment subsystem 114, and then passes tothe pressurizing subsystem 120 via line 116. Upon pressurization, a feedfluid line 122 conveys pressurized feed fluid from the pressurizingsubsystem 120 to the filter modules 130; a permeate collection line 132conveys depressurized permeate from the filter modules 130 to theholding tank 150; a waste fluid collection line 134 conveys pressurizedwaste fluid from the filter modules 130 to the energy recovery subsystem140; and a waste fluid discharge line 142 conveys depressurized wastefluid from the energy recovery subsystem 140 away from the system 110.

Also analogously to FIG. 1, it is contemplated that the feed fluid ofFIG. 2 may be any fluid amenable to treatment by filtration. In a greatmany instances the feed fluid will comprise water, or at least anaqueous solution such as such as salty or briny water. In otherinstances, the feed fluid may comprise a food, such as orange juice, orperhaps a petroleum intermediary that requires purification.

Quite unlike the filtration system 10 of FIG. 1, however, the filtrationsystem 110 of FIG. 2 contemplates that the various filter modules 130,and at least portions of feed fluid line 132, permeate collection line132, and waste fluid collection line 134 are all at least substantiallycontained within an outer casing to form a large tube assembly 170. Inone contemplated form of such coupling, the modules are seriallydisposed in an end-to-end fashion in production modules 160, with thecontinuous casings of the modules forming the casing of the large tubeassembly, and feed fluid flowing sequentially through upstream modulesto reach downstream modules. In other contemplated embodiments, at leastsome of the filter modules 160A, 160B are disposed parallel to oneanother within an outer casing of the large tube assembly, such thatfeed fluid flows through the lumen of the outer casing, and reachesindividual filter modules without necessarily passing through otherfilter modules. Still other embodiments (not shown) contemplate thefilter modules disposed in an outer casing such that the feed fluidflows to the filters in some combination of serial and parallel flow.

Production modules 160 may advantageously be similar in many respects tothe production modules 40 described in the WO 98/09718 publication,although here there is less constraint on the diameter than previouslycontemplated. In addition, the production modules 160 are contemplatedto be disposed in any relationship to vertical, including vertical,off-vertical, and even horizontal. As such, the large tube assembly 170may be disposed more or less horizontally on, above or below the surfaceof the ground, or in some other configuration such as a partially burieddisposition. In other contemplated embodiments, for example, the largetube assembly 170 may be set into a shallow well, perhaps less than 100or even less than 50 feet deep. In still other embodiments, the largetube assembly 170 may be disposed within or as part of a tower, hillsideor mountain. In yet another aspect, multiple large tube assemblies 170may be coupled together to form a field of assemblies (not shown), inany combination of dispositions.

Turning in greater detail to the pressurizing subsystem 120, it iscontemplated that any pump or pump system which provides adequatepumping volume and pressure may be employed in filtration system 110 topressurize the feed fluid. This includes positive displacement pumps,impeller pumps, head pressure devices, and many others. On the otherhand, some pumps and pumping systems will be more efficient than others,and such pumps and systems are particularly contemplated. A particularlyefficient pumping system is a two stage turbine pump, such as thatdepicted in FIG. 2. Here, feed fluid flows first to a relatively lowpressure turbine 120A, and then on to a relatively high pressure turbine120B. The low and high pressure turbines 120A, 120B may advantageouslyderive power from a single drive shaft 120C and motor 120D, althoughother embodiments having multiple drive shafts and/or multiple motorsare also contemplated.

Energy recovery subsystem 140 may take many different forms, includingpositive displacement devices (not shown) and turbine devices 140A suchas that shown, or a pelton wheel (not shown). In FIG. 2, for example,energy recovery subsystem 140 incorporates a turbine 144, which receivespressurized waste fluid from the production modules 160.

Energy recovery subsystem 140 is also preferably modularly coupled tothe pressurizing subsystem 120. In the particular embodiment of FIG. 2,modularization occurs by disposing both pressurizing subsystem 120 andenergy recovery subsystem 140 in a common power module 165, and furtherby utilizing the pump drive shaft to drive shaft 120C to transfer powerfrom the energy recovery subsystem to the low and high pressure turbines120A, 120B. In alternative embodiments, modularization may also occur bydisposing the pressurizing subsystem 120 and the energy recoverysubsystem 140 in separate power modules (not shown), which mayadvantageously be coupled by a common drive train.

There are numerous contemplated advantages to modularization.Modularization of the filters and flow lines into production modules,for example, is highly advantageous because it facilitates constructionof filtration systems which are physically disposed in a serial fashion,but are fluidly disposed in a parallel fashion. Such systems areinherently cost effective to build and maintain relative to traditionalsystems such as that depicted in FIG. 1. Modularization of thepressurizing and energy recovery subsystems is also advantageous from acost effectiveness standpoint. Among other things, such power modulescan be readily inserted and replaced in a given filtration system, andcan be substituted interchangeably with corresponding modules in a fieldof such filtration systems.

Some of these advantages can be more readily visualized fromconsideration of FIG. 3. In FIG. 3 a field 200 of filtration systemscomprises a first micro-filtration system 202, a second,ultra-filtration or non-filtration system 204, and a third,hyper-filtration or reverse osmosis system 206. Many of the parts mayadvantageously be modularized to enhance interchangeability andcost-effectiveness. For example, each of the filtration systems may havea pretreatment subsystem 214A, 214B and 214C, which in this case may bean ultra-violet or other bactericidal unit. Feed fluid for all of thefiltration systems 202, 204 and 206 in the field 200 is provided by well209, and is pumped to the first pretreatment subsystem 214A by pump 208.The feed fluid then passes to the first filtration system 202 via line216A, where the feed fluid is filtered in production modules 260A. Wastefluid leaves the first filtration system 202 via line 234A. Permeatefrom the first filtration system 202 is carried to the second filtrationsystem 204 via line, where further filtration occurs in productionmodules 260B. Waste fluid leaves the second filtration system 204 vialine 234B. Permeate from the second filtration system 204 is carried tothe third filtration system 206 via line 216C. At the third filtrationsystem 206, the relatively purified fluid is pressurized by pressurizingsubsystem 220, and is further filtered occurs in production modules260C. Waste fluid leaves the third filtration system 206 via line 234C.Permeate from the third filtration system 206 depressurized using energyrecovery subsystem 240, and then passes to holding tank 250.

Of course, the arrangement of systems set forth in FIG. 3 is exemplaryonly, and many other arrangements are contemplated. For example, FIG. 3depicts a field 200 in which a feed fluid is progressively more filteredacross several serially arrayed filtration systems. In alternativeembodiments it may be more appropriate to filter a feed fluid only once,so that the various filtration systems act in parallel rather thanseries. In yet additional alternative embodiments, a field may employnumerous sources of feed fluid, such as via multiple wells as opposed toa common well. In still further alternative embodiments, the variousfiltration systems may be disposed in differing attitudes relative tothe landscape. For example, some of the systems may be set mostlyunderground, while others may be near ground level, or disposed in atower.

Thus, specific embodiments and applications of a filtration system witha modularized energy recovery system have been disclosed. It should beapparent to those skilled in the art, however, that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. For example, it isparticularly contemplated that any or all of the various pumpscontemplated, including pumps employed in the pressurization and energyrecovery subsystems, herein may or may not be submersible.

The inventive subject matter, therefore, is not to be restricted exceptin the spirit of the appended claims. Moreover, in interpreting both thespecification and the claims, all terms should be interpreted in thebroadest possible manner consistent with the context. In particular, theterms “comprises” and “comprising” should be interpreted as referring toelements, components, or steps in a non-exclusive manner, indicatingthat the referenced elements, components, or steps may be present, orutilized, or combined with other elements, components, or steps that arenot expressly referenced.

I claim:
 1. A filtration system comprising: a pressurization subsystemthat pressurizes a feed fluid; an elongated outer casing in which aredisposed at least one inlet, at least two fluid outlets and a pluralityof elongated filtration modules, each of the filtration modules havingan opening through which the pressurized feed fluid flows into themodule, and a filter that cooperates with the pressurized fluid toproduce a pressurized waste fluid and a low pressure filtrate; whereinthe modules are mechanically coupled in series and at least some of themodules are fluidly coupled in parallel; a mechanical pump that impartspressure to the feed fluid at the filtration modules and thereby to thewaste fluid; and an energy recovery subsystem that recovers energy fromthe waste fluid that was imparted by the pump.
 2. The filtration systemof claim 1 wherein the pressurization subsystem is mechanically coupledto the energy recovery subsystem such that energy derived from theenergy recovery subsystem is used to drive the pressurization subsystem.3. The filtration system of claim 2 wherein the pressurization subsystemcomprises a turbine.
 4. The filtration system of claim 2 wherein theenergy recovery subsystem comprises a turbine.
 5. The filtration systemof claim 2 wherein both the pressurization subsystem and the energyrecovery subsystem comprises turbines.
 6. The filtration system of claim2 wherein the pressurization subsystem is mechanically coupled to theenergy recovery subsystem via a common drive shaft.
 7. The filtrationsystem of claim 2 wherein at least one of the pressurization and energyrecovery subsystems include a submersible pump.
 8. The filtration systemof claim 1, wherein the energy recovery subsystem recovers the energyfrom the waste fluid after the waste fluid exits the outer casing.